1. Field of the Invention
The present invention relates generally to a cooking process and, more specifically, a process for pre-heating a hydro-fuel and using the fuel with a barbecue grill having a flaming or catalytic glowing combustion mode that produces both heat and in-situ super-heated steam during combustion of hydro-fuels. Hydro-fuels are relatively volatile alcohol or hydrocarbon liquid fuels containing miscible water or water-in-oil micro-emulsions. The present invention relates to hydro-fuel cooking devices applicable for direct cooking of both meat and vegetables.
2. Description of the Prior Art
With respect to barbecue grills, it is a common practice to provide either gas or charcoal as a fuel source for the grill. Gas-fired barbecue grills mainly use liquefied propane gas (LPG). Hot gases from the flames heat the food items that are placed directly on the food support grid. In modern barbecue grills, non-combustible materials such as lava stones are used as a heat transfer media for uniform heating of food items. In charcoal grills, radiation from the glow of the hot coals heats the food item. The prior art contains extensive improvements in barbecue grill designs including a variety of burner designs, heat deflecting devices, surface cleaning strategies, and improvements to food support systems. However, the present invention is novel in that it provides a grill produces both heat and in-situ super-heated steam during combustion of hydro-fuels fuels that is used in cooking foods.
The use of the hydro-fuel alcohol specifically as a traditional fuel source in cooking stoves (or an indirect cooking device) is well known and is not reviewed here. A reference to the use of fuels other than common LPG gas or charcoal includes a solidified or semi-solidified alcohol. The U.S. Pat. No. 5,143,046 to Koziol teaches the use of gelled alcohol or a hydrocarbon type fuel in a barbecue grill. The methodology resembles the common food warming method that uses gelled alcohol commercially known as STERNO. The flame is diffusion type unlike the LPG premixed flame generally utilized in barbecue grills. The fuel vaporization rate is adjusted by varying the heat-exposed area of the solid fuel. In this surface combustion process, water, being the less volatile component, remains in the bottom of the gelled fuel reservoir. The present invention uses gasified premixed combustion and differs from this invention by bringing the water into the flaming region and producing continuous super-heated steam.
The U.S. Pat. No. 5,189,945 to Hennick relates to a water-cooled barbecue grill. Hennick teaches the use of circulating water from a reservoir to cool the cooking surface to prevent food from sticking to the surface. Food in the pans is cooked by heat from the water in the reservoir. The author claims the superiority of this barbecue grill based on the moist cooking which reduces food from crumbling and leaves the food tender. The present invention differs from Hennick in that super-heated steam created during combustion of hydro-fuels is directly applied in cooking foods.
One important obstacle to overcome in using liquid fuel burners is the problem of cold-starting the burning of the liquid fuel. This problem occurs due to condensation of atomized liquid fuel inside the fuel-air premixing tube before the mixture reaches the burner tip before the initial ignition of fuel. However, once the burner system is warm enough, the mixture will usually vaporize and burn without any problem. Historically, several approaches have been reported to overcome this problem. These approaches include pre-heating the burner system with gelled alcohol (also called STERNO), a burning wick soaked in a liquid fuel, a fire starter, electrical pre-heaters and so on. The U.S. Pat. No. 5,080,580 to Clapp teaches a method of using a pressurized liquid fuel with a minor amount of hydrocarbon gas as a propellant. The propellant-air mixture is fed into the combustion chamber and ignited easily, followed by the main liquid fuel. This invention teaches a much easier and reproducible method of eliminating the cold-start problem.
This invention provides a novel process of grilling that solves many of the deficiencies in the prior art by utilizing combustion of a new class of fuel compositions, which contain miscible water referred to as xe2x80x9chydro-fuels.xe2x80x9d A preferred embodiment uses fuel-grade ethanol containing a desired amount of water. Unlike petroleum products, ethanol is obtainable from renewable resources. The ethanol-water hydro-fuel produces in-situ steam for direct cooking in barbecue grills. Alternatively, alcohol may be the selected hydro-fuel and is particularly advantageous because of its low explosion hazard and stability in transport and storage. Unlike pressurized LPG, alcohol fuel is not pressurized during storage and transport, thus avoiding pressurized gas cylinders and increasing safety. The fuel tank is pressurized only before cooking. The absence of suffocating fumes and the generally low danger level in case of accidental leakage of the fuel makes the hydro-fuel user friendly.
More specific advantages of the present invention are provided by the continuous steam produced from in-situ combustion. The in-situ steam provides a moist cooking atmosphere, reduces cooking time, prevents food from crumbling, leaves a cleaner grill surface, and adds taste and tenderness to the directly cooked food.
Combustion of hydro-fuels containing water produces heat as well as steam. This steam is super-heated to flame temperatures. Along with convective heat from hot gases, the steam directly contacts the food item placed on the grill. This invention provides ways to improve the cooking method by using a new fuel composition and conceptual modifications designed to achieve the unique features indicated above.
Further, the present invention combines both heating and continuous steam generation in a single process, and thus eliminates the need for a separate steam chamber. The steam is produced continuously and is applied uniformly to the surface of the food. The steam provides a controlled temperature environment and hence gives a better taste for directly heated food. Because of use of cleaner combustion products, the method can be used for both indoor and outdoor cooking either in barbecue grills or normal cooking as a stove.
Accordingly, a first object of this invention is to provide a cooking device fueled by hydro-fuels that produces both heat and steam during combustion in a gas-fired grill. Hydro-fuels are relatively volatile alcohols or hydrocarbon liquid fuels containing miscible water or water-in-oil micro-emulsions. A preferred embodiment uses pressurized fuel-grade ethanol containing a desired amount of water as a source of fuel.
Another object is to retrofit a typical gas fired barbecue grill with a liquid fired burner by installing a suitable pre-heating tube or a coil just above the burner rim. The pre-heating coil vaporizes the liquid fuel before it is injected into the mixing chamber. A provision for drainage of condensed liquid inside the mixing tube is provided.
Another object of the invention is to provide a cooking device that can be used for both indoor and outdoors cooking of meat and vegetable items. For example, ethanol, being an oxygenated fuel, bums cleaner than any other hydrocarbon fuel such as methane, ethane, propane or butane. Hence, ethanol combustion is acceptable for indoor cooking.
Another object is to provide a cooking device that can be used both as a barbecue grill and a cooking stove. This objective can be achieved by using the cleaner burning ethanol, which is acceptable for direct heating of food. Campers do not want to cook steaks, hamburgers, or hot dogs for every meal. Many foods, particularly breakfast foods such as oatmeal, eggs, and corn, and a variety of vegetable items taste better when cooked over direct heat from a stove. Thus, it is desirable to provide a portable outdoor cooking apparatus that is capable of operating as both a barbecue grill and a stove using a single burner.
Another object of the present invention is to provide a barbecue grill that does not produce an open flame. A flameless combustion process may be achieved by inserting a catalytic wire mesh at the combustion zone. In the presence of a combustion catalyst surface, the flaming reactions will be shifted to a glowing surface combustion. The flame will completely disappear. This will reduce the chances of accidental fires. Catalytic combustion also provides cleaner combustion products. The heating is uniform because of infrared radiation.
Another object is to provide a barbecue grill with an option to collect fat and other condensates produced, including condensed steam during cooking. A concave plate is placed under the food support grid. The plate has a drip or a drain valve. Excess condensates that are collected can be drained if desired.
Another objective is to provide a barbecue grill where the surface remains relatively clean after cooking. Cleaning the grill surface is always a problem because it tends to become encrusted with food condensates, burner grease, and bits of food. Another problem associated with barbecue cooking is that some food types tend to crumble when cooked on thin metal rods. Conventional barbecues do not provide any means for steam cooking of meat or vegetables.
Yet another object is to eliminate the cold start problem generally encountered in liquid fuel ignition. This problem occurs due to condensation of atomized liquid fuel inside the fuel-air premixing tube before the mixture reaches the burner tip. However, once the burner system is warm enough, the mixture will usually vaporize and burn without any problem. The cold-start ignition problem is eliminated by first igniting the mixture inside the fuel-air mixing chamber, followed by an ignition at the burner tip.